The invention relates to battlefield radiation detectors or dosimeters of the type which employ a biased solid state crystal, for example a cadmium telluride crystal as the radiation detector or crystal counter. Such detectors are useful in protecting personnel from overexposure to radiation from fallout following the explosion of tactical nuclear weapons. The prompt initial radiation (PIR) of these nuclear weapons comprises a short powerful gamma ray pulse and a fast neutron component, both emitted simultaneously during the explosion of the weapon. The gamma ray component travels at the speed characteristic of electromagnetic radiation, namely at the velocity of light (c) in a vacuum and only slightly slower in the atmosphere. The neutrons are produced with a range of initial velocities all of which are much smaller than c, and thus at points outside the radius of total destruction, the gamma ray pulse arrives first, followed by the high intensity fast neutron pulse which has been lengthened by the aforementioned velocity spread of its individual neutrons. The fast neutron pulse can damage a biased crystal radiation counter more severely than an unbiased one. In some cases a biased crystal can be destroyed by the fast neutrons of the PIR, however even an unbiased crystal will suffer loss of charge collection efficiency from these fast neutrons. The invention provides a circuit which responds to the passage of the high intensity gamma ray pulse to automatically remove the crystal counter bias for a short time sufficient to permit the fast neutron pulse to pass by in a less harmful manner, after which the crystal counter bias is restored and the crystal can resume its function of detecting radiation due to fallout.